1. Field of the Invention
The present invention relates generally to a co-pyrolysis process for forming carbonized composite bodies in which co-pyrolysis of organic fibrous and matrix components is effected during initial pyrolization. More particularly, the invention relates to a co-pyrolysis process for improving interfacial bonding of composite bodies by combining fibrous precursors, or reinforcements with a controlled pre-shrink state, with an appropriate matrix to insure shrinkage matching during processing.
2. Description of the Prior Art
Carbonized composite bodies, especially reinforced carbon-carbon composites, are subjected to many modern industrial applications, particularly in the fields of aerospace and aviation. As noted in U.S. Pat. No. 4,500,602, reinforced carbon-carbon composites that are generally constructed of fibers and bound by carbon matrix produce a material having excellent structural properties. The precursors for carbonaceous fibers are polyacrylonitrile, rayon, or pitch based fibers while the carbon-carbon impregnation materials are phenolic, furfuryl or pitch based materials. However, reinforced carbon-carbon composites are subject to degradation in high temperature oxygen environments unless, in accordance with the teachings of the aforesaid disclosure a protective coating is provided which comprises a first coating layer of silicon carbide and a second layer of sputtered zirconium oxide.
A method of fabricating carbon composites involving both resin and chemical vapor deposition (C.V.D.) steps is disclosed in U.S. Pat. No. 4,490,201 whereby a suitable carbonaceous binder, such as phenolic resin, polyimide resin, or a like material is applied in a limited amount to a partially carbonized fibrous material, such as polyacrylonitrile, wool, rayon, or pitch felt prior to pyrolization and C.V.D. of pyrolytic carbon densification steps. A major disadvantage of the C.V.D. method is that some form of expensive and bulky shaping fixture is required to hold the substrate materials in the desired configuration until sufficient pyrolytic carbon has been deposited to rigidize the fibrous structure.
Other patents of general interest are U.S. Pat. Nos. 4,234,650; 4,029,829; 3,991,248; 3,462,340; and 3,233,014.